Piston device for a valve



FIG. 1 is a perspective view of piston device for a valve;

FIG. 2 is a top view of FIG. 1;

FIG. 3 is a bottom view of FIG. 1;

FIG. 4 is a right side view of FIG. 1; and,

FIG. 5 is a left side view of FIG. 1.

The broken lines shown in the drawings depict portions of the piston device for a valve that form no part of the claim. 

CLAIM The ornamental design for piston device for a valve, as shown and described. 